Verse 2

2. And to him,  the Lord said,  "Know this knowledge by means of faith,  yoga,  devotion and meditation.  Not by works,  nor by progeny,  nor by wealth,  but by renunciation,  some attained immortality".

"the Lord said,  Know this knowledge by means of faith,  yoga,  devotion and meditation"

As stated above,  this subtle or "secret" knowledge,  can only be known and understood by those with faith and love of the truth for truths own sake.  Higher knowledge has to be sought with a vision that is focused through disciplined practices ("yoga") led by meditation and inner enquiry.  This process takes time and dedication and is a path for the devoted only.

"Not by works,  nor by progeny,  nor by wealth"

Very quickly our true purpose in life is covered by the unreal values of the majority which arise through the delusion of duality,  guided by material face values,  which deny the growth of the subtle seed of true purpose,  allowing the false values to delude us into believing our purpose is the material "success" of accumulating worldly knowledge,  wealth fame and power.
It is the delusion of duality that causes the seeing of others as separate existences from ourselves.  Duality is the forgetting of the underlying unity of all existence,  this forgetting gives rise to the fear of inadequacy that causes the need or desire to collect material wealth for protection and status.  It is only through duality that inadequacy can be experienced,  inadequacy imagines the need for work and increase.  The desire for progeny is the desire to thrive with love for material prosperity within this creation that was itself caused through desire.
The meaning here is that the higher Knowledge that transcends this world cannot be seen or achieved while flourishing through material acquisition. 

"but by renunciation,  some attained immortality"

This verse confirms that the unreality of the transient world needs to be renounced.  It is through a yoga of purification and meditation that the real,  the eternal is seen.  It is not by the achievements of wealth,  work or progeny but through the renunciation of this unreality we achieve the higher knowledge that leads to immortality through Self Realisation.

The meaning here is that this knowledge is not obtainable through material or worldly means.  The reality is that the highest Truth transcends this Creation.  One needs to renounce this world to reveal the Truth.